What is not made clear though is the fact that current consumption exceeds net primary production by about 3x on the earth as a whole. (This difference is largely made up for by fossil fuels.) This article, Can the earth’s plants keep up with us? is clearer on that point.

The ratio of human consumption to regional net primary productivity could be an indicator of locations that are particularly vulnerable to supply disruptions, for example, as a result of natural disasters or civil unrest. Combined with models of the impacts of climate change, these models could also help countries predict the biosphere’s ability to sustain their population’s consumption levels in the future.